JPH04307613A - Electronic equipment - Google Patents

Abstract

PURPOSE:To prevent the malfunction of an electronic equipment that is caused by the sudden drop of the battery voltage at the time a power supply is turned on by interrupting the supply of power to a load circuit when the battery voltage is lower than a prescribed level when the ON key of a power switch is operated. CONSTITUTION:When the ON key 20 of the power switch is operated, a flip-flop 19 is set and then and AND gate 13 is opened. Thus the transistors TRs 16 and 17 are conducted and the voltage of a battery 7 is supplied to a voltage stabilizing circuit 18 via the TR 16. The circuit 18 boosts the input voltage and supplies the drive voltage with stability. However in a voltage range lower than a prescribed level where a message is displayed to show the drop of voltage set when the supply of power is interrupted, the voltage is not recovered due to the interruption of the power supply. Thus the output of a voltage detection circuit 8 is kept at an L level. Therefore the gate 13 never opens even if the key 20 is operated next. Thus both TRs 16 and 17 are never conducted and the drive voltage is not supplied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic equipment that can be driven by batteries.

0002

2. Description of the Related Art Recently, electronic devices such as word processors and personal computers have been developed to be small in size and have low power consumption, and are configured to be powered by batteries. These devices are equipped with a battery voltage detection circuit, and when the voltage drops to a predetermined level, a message notifying battery replacement is displayed on the display to alert the user (for example, (See Publication No. 146227).

0003

[Problem to be Solved by the Invention] By the way, at the stage when a message to replace the battery is displayed, the battery is still usable, so the user generally continues to use the battery until it malfunctions due to voltage drop. Yes, in that case, if you replace the battery after use, you will be able to use it from next time without any problems. However, I simply turned the battery off without replacing it.
In the event of an FF, the voltage that had dropped due to the characteristics of batteries, especially dry batteries, when the device is not in use will temporarily recover to above the reference voltage, so that when the power is turned on the next time it is used,
Although the device is temporarily set to operating state, the power is turned off.
Due to N, the battery voltage drops rapidly, resulting in problems such as malfunctions and, in the worst case, memory contents being destroyed.

0004

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes a means for detecting battery voltage, a switching means for controlling power supply to a load, a power switch, and a power supply. If a predetermined voltage is not detected by the battery voltage detection means when the switch is turned on, the switching means is made non-conductive to cut off power supply to the load.

[0005]

[Operation] Since the present invention is constructed as described above, when the battery voltage has dropped below a predetermined voltage, the power switch is turned on.
Since power is not supplied even if the battery voltage drops, malfunctions due to a drop in battery voltage can be prevented.

[0006]

[Embodiments] Hereinafter, embodiments of the present invention will be explained based on the drawings.

[0007] The electronic device has a control circuit (1) composed of a microprocessor, a control circuit (1), and a signal bus (2).
A keyboard (3), a memory (4), a display (5), and a power supply circuit (6) that supplies driving voltage to each part are connected to
), the control circuit (1) is connected to the keyboard (3).
) Data is read from and written to the memory (4) based on key signals from the memory (4), and key-input data or processed data is displayed on the display (5). Since these operations are well known, a detailed explanation will be omitted, and the power supply circuit (6), which is a feature of the present invention, will be explained in detail.

[0008] (7) is a power supply battery for driving, which outputs a voltage of 4.5V. (8) (9) is a voltage detection circuit that detects the voltage of the battery (7), and (8) is a voltage detection circuit that detects the voltage of the battery (7).
When the battery voltage falls below 2.8V, the output is inverted from H level to L level, while (9) is configured so that when the battery voltage falls below 2.8V, the output is inverted from H level to L level. (10) is a gate circuit to which the output of the voltage detection circuit (8) is supplied;
Consists of an R gate (12) and an inverter (14),
A voltage detection circuit (8) is connected to one input of the ND gate (11).
output is supplied, and the other input is supplied with a drive voltage (V
cc) is supplied via an inverter (14). The output of the AND gate (11) and the driving voltage (Vcc) are supplied to the OR gate (12), and the output of the OR gate (12) is supplied to one input of the AND gate (13), and the output of the OR gate (12) is supplied to the other input. A flip-flop (1
9) is supplied with the set output (Q).

(15) is a transistor (16) (17)
A switching means consisting of a transistor (16
), a battery (7) is connected to the emitter of the transistor (17
) is connected to the output of the AND gate (13), and the output of the AND gate (13) controls the conduction of the transistors (16) and (17). (19) is a flip-flop that is set by operating the ON key (20) of the power switch and reset by a signal from the control circuit (1), and its set output (Q) is connected to the AND gate (13).

(21) is a 3V backup battery that retains the contents of the memory (4) when the power switch is OFF, and outputs a backup voltage (Vb) through an OR circuit consisting of the drive voltage (Vcc) and diodes (22) and (23). are doing. This backup voltage (Vb) is applied to the voltage detection circuit (8) and gate circuit (10) even when the power switch is OFF.
and a flip-flop (19) to keep it in operation. Further, the output of the voltage detection circuit (9) is supplied to the control circuit (1) to instruct a voltage drop.

Next, the operation of the present invention constructed as described above will be explained based on the battery voltage state diagram shown in FIG.

First, when the power is turned off, the flip-flop (19) is reset and the set output (
Q) is at the L level, the AND gate (13) is closed, the switching transistors (16) and (17) are non-conductive, and the voltage of the battery (7) is not supplied to the voltage stabilizing circuit (18), so that the drive voltage ( Vcc) is not generated. However, during this time, the backup voltage (Vb) is still generated by the backup battery (21), and the contents of the memory (4) are retained, and the backup voltage (Vb) is applied to the voltage detection circuit (8) and the gate circuit (10). When the voltage of the battery (7) is 3.2V or higher, an H level signal is output from the voltage detection circuit (8), and an AND signal is output via an AND gate (11) and an OR gate (12). An H level signal is supplied to one input of the gate (13).

In this standby state, when the ON key (20) of the power switch is operated, the AND gate (13) is opened by setting the flip-flop (19), so that the transistors (16) (17) is turned on and the voltage of the battery (7) is supplied to the voltage stabilizing circuit (18) via the transistor (16). Voltage stabilization circuit (1
8), the input voltage is boosted and stabilized to create a 5V drive voltage (
Vcc). As a result, each part has a driving voltage (Vc
c) is supplied, and each part such as the control circuit (1) is set to an operating state. On the other hand, when the driving voltage is generated, the AND gate (11)
is closed, but the driving voltage (Vcc) continues to be supplied to the AND gate (13) via the OR gate (12), so the switching transistors (16) and (17) are kept conductive and the driving voltage (Vcc) Continuously outputs.

Next, the operation when the voltage of the battery (7) decreases due to use of the device will be explained. As shown in Figure 2, the voltage of the battery (7) is in the range (I) of 4.5V to 3.2V.
In this case, the output of the voltage detection circuit (8) is at H level, but
In the range (II) where the voltage decreases from 3.2V to 2.8V,
The output of the voltage detection circuit (8) is inverted from H level to L level. Meanwhile, during this period, the output of the voltage detection circuit (9) remains high.
maintained at the level. However, the voltage of battery (7) is 2
．． In the range (III) where the voltage drops to 8V or less, the output of the voltage detection circuit (9) becomes L level, which causes the control circuit (1
), the voltage drop is detected by the control circuit (1
) displays a message urging battery replacement on the display (5). Even if the battery voltage drops, the voltage stabilization circuit (18) is still generating a 5V driving voltage (Vcc) and the equipment will operate normally, so after the message is displayed on the display (5), It is also possible to use the equipment. However, if you continue to use the battery with a low voltage, the voltage stabilization circuit (18) will drop to about 2.5V.
may not operate properly, drive voltage (Vcc) may no longer be generated, the product may suddenly become inoperable, and the contents of the memory (4) may be destroyed, so if a voltage drop message appears, stop using the product as soon as possible. It is better to replace the battery after it has finished.

Next, the operation of turning off the power will be explained. In this case, when the OFF key provided on the keyboard (3) is operated, the control circuit (1) that has detected the key signal generates a control signal when the operation currently being processed is completed.
By resetting the flip-flop (19),
The AND gate (13) closes and the switching transistors (16) and (17) become non-conductive, cutting off the power supply. In this way, by cutting off the power supply to the load, the battery (
7) will be slightly restored, so if the power supply is cut off in the position of range (II), i.e. before the message is displayed on the display (5), the voltage will rise above 3.2V. Since the voltage is recovered, the output of the voltage detection circuit (8) is inverted to H level again, and when the ON key (20) is operated next, the AND gate (13) is opened and the drive voltage is adjusted in the same manner as described above. (Vcc) is generated and becomes operational. However, if the power supply is cut off in the range (III) after the message is displayed on the display (5), the battery voltage will not be restored to 3.2V or higher even if the power supply is cut off, so the voltage The output of the detection circuit (8) remains at L level. Therefore, the next time you try to use the ON key (2
0) is operated, the AND gate (13) is not opened, so the switching transistors (16) and (17) are not conductive and the drive voltage (Vcc) is not supplied.

FIG. 3 shows another embodiment, in which the control circuit (1)
determines the output of the voltage detection circuit (8) and the ON key (20)
At the same time, the switching transistor (1
6) The conduction control of (17) is performed. Therefore O
The control circuit (1) detects that the N key (20) is operated.
) checks the output of the voltage detection circuit (8) in step (S1) and determines whether the battery voltage is above a predetermined voltage, and if it is below the predetermined voltage, the control circuit (1) does not operate at all. Return to standby state. However, if the voltage is higher than the predetermined voltage, the control circuit (1) proceeds to step (S2), turns on the switching transistors (16) and (17), and supplies the drive voltage (Vcc), and then proceeds to step (S3).
The process proceeds to step 1 and performs a predetermined processing operation. Each time one process is completed, the control circuit (1) checks the output of the voltage detection circuit (8) in step (S4) to detect whether the battery voltage is higher than a predetermined voltage. If the voltage is above the specified voltage, step (
Returning to S3), the process is repeated, but when it is detected that the voltage has dropped below the predetermined voltage, the control circuit (1) returns to step (S5).
The process proceeds to step S7, where a message indicating battery voltage drop is displayed and a predetermined period of time has elapsed, the process proceeds to step S7, where the transistor (16
) (17) is made non-conductive to cut off the power supply and return to the standby state. In this case as well, if the battery voltage has decreased, power will not be supplied even if the ON key is operated, so malfunctions due to a decrease in battery voltage can be prevented.

[0017]

As described above, the electronic device of the present invention is configured to cut off the power supply to the load circuit if the battery voltage is below a predetermined voltage when the ON key of the power switch is operated. This prevents equipment malfunctions caused by a sudden drop in battery voltage when turned on, and is highly effective when applied to battery-powered equipment.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of the present invention.

FIG. 2 is a schematic diagram showing battery voltage states.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of FIG. 3;

[Explanation of symbols]

1 Control circuit 6 Power supply circuit 7 Battery 8 Voltage detection circuit 18 Voltage stabilization circuit

Claims (1)

[Claims] Claims: 1. In a battery-driven electronic device, a means for detecting battery voltage, a switching means for controlling power supply to a load, a power switch, and a device for detecting the battery voltage when the power switch is turned on. 1. An electronic device comprising means for making the switching means non-conductive and cutting off power supply to the load when a predetermined voltage is not detected by the means.